Process of preparing furfuryl alcohol resins



The present invention advantageous process'for the production of an initial, fusible, soluble, furifuryl alcohol condensa- Patented 18,1947.

PROCESS OF'PREPARING FURFURYL .ALCOHOLRESINS 'William H; Adams, Jr., Newark, Del., as'sgnor to Haveg Corporation, Newark, Del., a corporation of Delaware g. No Drawing. Application August 3, 1944,

= Serial No. 547,971

relatesto a novel and tion product which may be converted into an infusible, insoluble, furfuryl alcohol resin characte'rized by hardness. toughness, and chemical resistance.v More particularly, the invention rej lates to a process by which the acid condensation of iurfuryl alcohol can be controlled so that furfuryl alcohol condensation products of desirable condensation of furiuryl alcohol has been suggested. butmy investi ation of the subject has shown that the condensation reaction has not been controllable for t e production of resins oi. desiredproperties. Thus. in order to obtain a resin characterized by hardness and toughness, a relatively large amount of strong acid is rev 15 Claims. (Cl. 260-67) quired. The use of such an amount of acid, however. is hazardous due to the violence of the reaction and the tendency for spontaneous conversion of the condensation productinto the iniusible, insoluble condition. For example, relatively concentrated sulphuric acid, when added' drop-by-drop to furfuryl alcohol. causes converf sion of the fur'i'uryl alcohol into the infusible,

insoluble resin around the acid dropsand may cause substantial conversion of the entire prod-- the conversion of the initial condensation product is of poor duality and is not satisfactory for commercial usesdue to its weak nature and soft n nkv condition, These diiliculties. particularly the violent nature; of the reaction which has heretofore been encountered when aproductof. opti-, I

mum properties hasbeen' sought. have retarded the commercialization of'furfuryl alcohol resins, in spite of their'known superior hardness. toughness. and-chemical resistance as compared to most heat-converted'resins.

In addition. such furfuryl alcohol resins as have been obtained heretofore have often not possessed maximum strength and have been susceptible to appreciable shrinkage. As the result of my investigations; it has been found that the acid condensation of furfuryl alcohol involves an ini 2 termolecular condensation with the accompanying liberation of water, and that the liberated water, together with the uncombined furiuryl alcohol and other volatile components, is tenaciously held in the furfuryl alcohol condensation.

product. The presence of water and other nonresinophoric materials in the initial furfuryl alcohol condensation product at the time of the conversion of the product into the infusible, insoluble stage results in the aforesaid disadvantageous properties. Thus. these materials may be trapped in the resin during the conversion and a product of less than the maximum possible strength is then obtained, In addition, these materials may volatilize during the conversion of the resin or they may volatilize over a period of time at room or elevated temperature, after the conversion of the resin, causing porosity and shrinkage of the product and the formation of checks and cracks.

One object of the present invention is to provide a process for the production of a fusible, soluble, furfuryl alcohol condensation product by which the difiiculties heretofore encountered in the acid condensation of furfuryl alcohol may be avoided and a product of desired properties may be readily obtained.

A further object of the invention is to provide a process for the acid condensation of furfuryl alcohol which is controllable to provide an initial condensation product which may be converted into aninfusible. insoluble product characterized by hardness, toughness, and chemical resistance.

Still another object of the present invention is to provide a' process for the production of a fusible, soluble, relatively anhydrous furiuryl alcohol condensation product capable of conversion into an infusible, insoluble product of maximum strength and of low volatile content, and consequently of low porosity, and low shrinkage.

Other objects will be apparent from a consideration of this specification and the claims.

In accordance with the present invention, the condensation reaction of furfuryl alcohol is controlled by the'use of a solution of the acid catalyst in furfural (furfuraldehyde), In other words, instead of following the usual practice and adding the acid catalyst directly to the furfuryl alcohol which, as pointed out, results in a diflicultly controllable reaction, the acid catalyst is first dissolved in furfural andthe furfural solution of the catalyst is then added to the furfuryl alcohol. The introduction oi. the acid to the furfuryl alcohol in a solution of furfural is to be contrasted to its addition in wateror other solvent furnishing an added impurity which either anaose requires subsequent removal or remains in the resin to detract irom its qualities. As pointed out previo usly. if an attempt is made to avoid the use of water or other solvent, the undiluted acid will not mix satisfactorily with the furfuryl alcohol and an explosion or the conversion of the resin around the droplets will occur. The use of the solution of the acid in furfural, however, provides only a resiniforic additive since furfural itself forms a resin in the presence of acid, although at a much lower rate and requiring more acid than furfuryl alcohol. Hence in proceeding in accordance with the present invention the acid is diluted to a point which provides a controllable reaction without the introduction of any impurity of a non-resiniforic nature, the furfural itself becoming part of the resinous product.

By the use of the solution of the acid catalyst in furiural, the tendencies for too violent a reaction on the one hand and for an insufliciently acid reaction to furnish a product of desired properties on the other hand are avoided. The reaction to produce the initial furfuryl alcohol condensation product is controllable by cooling the reaction mix or by conducting the reaction under vacuum as will be discussed hereinafter. In addition, the initial products obtained are convertlble into infusible, insoluble resins of excellent hardness, toughness, and chemical resistance, and the process assures uniformity of the products obtained in production from run to run so that variations in the properties of the product may be avoided.

In the preferred embodiment of the invention, the initial condensation product obtained as the result of the controlled reaction is treated to reduce the water content of the product to a minimum to provide an initial product which can be converted into an infusible, insoluble resin of maxi-mum strength and of low porosity and shrinkage.

The acid catalyst employed is preferably a strong acid catalyst uch as sulphuric acid, phosphoricacid, sulphur chloride, and the like, since, as stated, resins of the-most desirable properties are obtained with the use of strong acid catalysts.

' However, the process is applicable for use with other acid catalysts, including the weak acids, such as maleic and oxalic acids. The amount of acid catalyst dissolved in the furfural will depend on the amount of acid to be employed in the catalysis of the furfuryl alcohol and on the amount of furfural which it is permissible to add to the furfuryl alcohol without deleteriously affecting the properties of the product. In most instances, it will not be desirable to add more than furfural to the furfuryl alcohol because as the amount of furfural increases above 3 this-percentage, the properties or the product tend to be deleteriously affected. In general, the amount of acid dissolved in.the furfural will not exceed 10% to 15% by weight based on thi A furfural and usually the furfural solution of the acid will be a 5% or weaker solution.

Referring to the amount of acid catalyst dissolved in the furiural to be added to the iurfuryl alcohol, the amount depends on whether the acid catalyst is a strong or a weak catalyst. In the case of a strong acid catalyst, the furfural solution will provide between 0.05% to 1.00% acid,

on the weight of the furfuryl alcohol. The solution of the catalyst in furfural may be mixed with the furfuryl alcohol in any desired manner, and the mixture is advantageously agitated durin the reaction.

The furfuryl alcohol to which the solution of the acid catalyst in furfural is added will heat up spontaneously in a short time, and the reaction is then controlled by cooling to a temperature below 100 C. to avoid spontaneou conversion of the resin-and an explosive reaction. Generally, the reaction is controlled between 40 to 80, and more specifically between C. and 70. The cooling may be provided by external cooling such as by ice, cold water, or brine or by conducting the reaction under vacuum to establish an equilibrium, as described and claimed in copending application Serial No. 556,657, filed Sept. 30, 1944. When the reaction is controlled by external cooling, the initial, fusible, soluble resin, after completion of the reaction which is indicated by the cessation of the liberation of heat, may be separated from a portion of the water and other material present, if desired, by any suitable procedure, for example, by allowing the reaction product to settle and by separating the layers by decantation, siphoning, centrifuging, and the like.

when the reaction is controlled by vacuum. a

vacuum, for example about 20 to 30 inches, is advantageously applied immediately after the addition of the solution of the catalyst in furfural. As the mass heats up due to the reaction, water is liberated, usually starting at a temperature in the neighborhood of C. to C. and at the same time heat is generated at a ratewhich d8! pends on the temperature. Under the vacuum, the water is quickly distilled pi! and the reacting mass is cooled by the evaporation of the water at a definite rate so that the temperature of the reacting mass during the active condensation of the turfuryl alcohol is maintained within controllable limits. An equilibrium or substantial equilibrium is quickly establishedwherein the rate of loss of heat from evaporation substan- .tially equals the rate of production of heat by the reaction of resinification'. 'ance of the equilibrium depends upon the rate of distillation and the amount and type of catalyst. As a result of theequilibrium conditions, water is smoothly distilled ofi and the reacting mass substantially maintained at its equilibrium Serial N0. 556,657, filed Sept. 30, 1944. After,

completion of the condensation reaction, the reaction mixture maybe used directl in the production of resinous products or the vacuum distillation may be continued, preferably under vacuum, to remove traces of water and other volatile matter ashereinafter described.

Unless the condensation product is rendered substantially free from acid, the initial resin obtained is a one-stage resin, that is, one which is convertible, due to the presence of acid therein, into an infusible, insoluble resin. If a two-stage resin is desired, the initial product is treated to counteract the efiect of .the acid. This is advantageously accomplished by adding a neutralizing agent to the reaction mixture or to the initial resin from which a portion of the water and other material has been removed in an The point of baltermination.

resin isnon-convertible byheat, and, in order to render it heat-convertible, additional acid must be added. g v Either the one-stage or two-stage resin thus obtained may be used in the production of molded or laminated products, molded products made 'by the so-called "Haveg process and other types of resinous products in accordance with standard procedures employed in the industry. The twostage resin may also be utilized to advantage in accordance with the disclosure of copending applicatlon'Serial No. 511,600, filed November 24,

1943, wherein the use of a latent catalyst for the conversion of a non-reactive furfuryl alcohol into the infusible, insoluble resin is..disclosed and claimed.

In accordance with the preferred embodiment of the invention, the initial resin obtained either by controlling the reaction by external cooling or by vacuum is subjected to distillation, advan-' .tageously under vacuum, to reduce the water and other non-resinophoric constituents of the prod uctin a low value. Generally, it will be desirable, .to distil a non-reactive initial resin but in the event the acid content of a reactive resin is relatively low and care is taken, such a resin may be subjected to distillation, although in most instances difliculties will be encounteredin obtaining an anhydrous resin due to the tendency of the reactive resin to polymerize spontaneously.

As has been pointed out, my investigations have'shown that water and other volatile substances are held tenaciously by the resin and that the presence of non-resinophoric materials in the initial resin results in a final converted product of less than maximum strength and one which is susceptible to shrinkage withthe' result that contain volatile material, the volatile material is resinophoric and hence the product will be substantially free from substances that will cause cracks, porosity and the like. The converted product is far more stable than is one which has not been subjected to distillation and is less liable to cracking and crazing. The volatile content of the initial resin will depend on the reaction conditions employed in the production of the initial resin, and the volatile content of .the initial resin after distillation and of the converted resin will depend, of course, on the conditions of the distillation and also to some extent on the nature of the initial resin distilled. In all cases, however, the volatile content ofv the resin will be greatly reduced by the distillation treatment and, while the distillation may be stopped at any point desired, it is preferably carried on until a substantially anhydrous resin is obtained. Aslillustrative of the reduction in volatile content of the product, an initial resin of a volatile loss of about to 40% or more may after vacuum distillation contain substantially no water and may have a volatile content of about 12% to which resin may be converted into an infusible, insoluble resin havin a volatile content of from about it being understood that there is a substantialreduction in each stage and that, in

general, thehigher the volatile content in the resin distilled, the higher will be the volatile content in other stages.

The distillation is conducted in any suitable still provided with a source of heat, such as a steam jacket, and advantageously equipped with an agitator. The temperature and time factors will depend on whether a vacuum is employed, the degree of vacuum if employed, the nature of the resin being distilled, and the volatile content of the product desired] While the initial] resin can be distilled, if desired, at atmospheric pressure, the use of a high vacuum is recom-' mended, for example, from 20 to 30 inches of mercury, more specifically 25 to 30 inches of cracks or checks may develop in the product.

For example, the 'resin prepared by controlling the reaction by external cooling and separated from a portion of the water and other material, as abovedescribed, contains a large amount of water and other volatile material; for example, such a resin may have a volatile loss of 25% to 40% .or more, as determined by spreading a three-gram sample of resin over the surface of a shallow dish of about two inches, diameter and heating without pressure for twenty-four hours at 150 C. The figures for volatile content hereinafter given are also based on this method of deminimum shrinkage, inother words, a substantially anhydrous resin. Although the resin may mercury. The temperature and time of treatment may vary from about 50 C. to 180 C. and from ten minutes to four or five hours respectively. This distillation is preferably carried out at about 26 inches to 28 inches of mercury to a temperature of about C. which require about thirtyfive minutes. In any particular distillation, the conditions thereof will be selected to obtain a.

' resin of the properties desired and, as stated,

advantageously one which hydrous.

When the condensation reaction has been is substantially ancontrolled by conducting the reaction under vacuum and a substantially anhydrous initial resin is desired, the vacuum distillation of the resin, preferably after neutralization, is advantageously continued in the still employed in the production of the condensation product until substantially all of the water has been removed.

The following examples are illustrative of the process of the invention, and while these examples include the step oi vacuum distillation to produce the substantially anhydrous resin, it is to be understood that this step may be omitted if desired and the initial condensation product may be employed directly in the preparation of the final, infusible. insoluble product.

Example I To 300 grams of furfuryl alcohol in a suitable flask, there was added 7.5 grams of a 10% solution-of sulphur chloride dissolved in furfural. In

and the resin was becoming viscous.

7 thirty-nine minutes, the temperature rose spontaneouslyto 80 C., whereupon the reaction mixture was cooled to about 65 C. by immersion of the flask in ice water and the reaction mixture was maintained at this temperature for thirtyeight minutes. distilled under a vacuum of 29 inches for twentyflve minutes. until the temperature rose to 88 C., at which point substantially all of the water had been removed. After cooling, the resin was moderately stiff and had a volatile content of 18.85% when dried in a shallow dish for twentyfour hours at 150 C. The substantially anhydrous resin polymerized very rapidly and could not be stored for any length of time. The initial resin upon subjection to heat was converted into a. hard resin with markedly elastic properties.

When the reaction mixture was neutralized prior to distillation, a non-reactive resin was obtained which could be stored indefinitely and after the addition of a small amount, for example .1% to .9% sulphuric acid, to, the neutralized distilled resin, the reactivity was re-established and a heat-convertible resin provided.

Example II To 400 grams of iurfuryl alcohol in a. two litre flask, there was added 20 grams of a solution of sulphuric acid in furfural. The mixture warmed up rapidly to boiling and was cooled to 55 C. by immersion of the flask in cold water. and the reaction mixture was maintained at this temperature for thirty minutes. The reaction mixture was distilled under vacuum as described in the preceding example and the initial resin was somewhat thinner than that obtained in Example I, butits curing was about the same. Furthermore, like the product of Example I, it could not be stored, but a non-reactive resin was obtainable by neutralization as described in connection with Example 1.

Example III 400 grams of i'urfuryl alcohol was placed in a two litre flask connected for vacuum distillation, and 12 grams of a 5% solution of sulphuric acid in furfural were added. Vacuum was immediately applied and in sixteen minutes, the temperature had risen to 58 C. and the reacting mass was boiling vigorously with water distilling oil. After fifty minutes, the temperature had risen to 79 C. At this point, the vacuum was broken and 22 grams of a 5% solution of barium hydroxide is. slight excess) were added. The distillation was continued for fifteen minutes and then the resin was removed from the flask and cooled. The resin remained fluid for several weeks and was substantially non-reactive even after many hours at 150 C. However, when 5 grams of a solution of sulphuric acid in furfural were added, the resin became potentially reactive and was converted to a solid, infusible, insoluble product when heated for five minutes at 150 C. The initial resin after the addition of the acid had a volatile content of 14.10%, determined 'as described in Example I, and at room temperature, it hardened in two days.

The polymerized resins obtainable in accordance with the present invention are characterized by excellent strength, together with toughness, and are distinctly superior to phenolic resins in these respects. In addition, they have a much greater range of chemical resistance than do phenolic resins, for example, they are re- The reaction mixture was then sistant to strong and weak bases and acids. to salts, and to a much wider range of solvents.

Considerable modification is possible in the selection of the conditions of the condensation reaction, as well as in the conditions of the distillation (if employed), without departing from the essential features of the invention.

I claim:

1. The step in the process of preparing an initial, fusible, soluble, furfuryl alcohol resinous condensation product which comprises adding to furfuryl alcohol a solution of an active acid catalyst in furfural, the amount of furfural not exceeding about 15% based on the weight of the furfuryl alcohol.

2. The step in the process of preparing an initial, fusible, soluble furfuryl alcohol resinous condensation product which comprises adding to furfuryl alcohol a solution of an active strong acid catalyst in furfural, the amount of iurfural not exceeding about 15% based on the weight of the furfuryl alcohol.

3.. The step of claim 1 wherein the amount oi strong acid catalyst added to the furfuryl 'alcohol is between about 05% and about 1.0% based on the weight of the furfuryl alcohol.

4. The process of preparing an initial, fusible,

soluble, furfuryl alcohol resinous-condensation product which comprises dissolving an active'acid catalyst in furfural, the amount of furfural not exceeding about 15% based on the weight of the furfuryl alcohol, adding said furfural solution of the catalyst to furfuryl alcohol, reacting said mixture to provide a furfuryl alcohol condensation product, and during said reaction cooling said reaction mix.

5. The'process of claim 4 wherein the acid catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about .05% and about 1.0% based on the weight of the furfuryl alcohol.

6. The process of preparing an initial, fusible, soluble, furfuryl alcohol resinous condensation product which comprises dissolving an active acid catalyst in furfural, the amount of furfural not exceeding about 15% based on the weight of the furfuryl alcohol, adding said furfural solution of the catalyst to furfuryl alcohol, and reacting said mixture under a vacuum to form a furfuryl alcohol condensation product while controlling the temperature of said reaction mix by a substantial balance between the loss of heat from evaporation and the production of heat by reaction.

'7. The process of claim 6 wherein the acid catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about .05% and about 1.0% based on the weight. of the furfuryl alcohol.

The process of preparing an initial, fusible, soluble, furiuryl alcohol resinous condensation product which comprises dissolving an active acid catalyst in furi'ural, the amount of furfural not exceeding about 15% based on the weight of the furfuryl alcohol, adding said furfural solution of the catalyst to furiuryl alcohol, reacting said 9. The process of claim 8 wherein the acid.

catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about 0.05% and 1% based on the weight of the aeiaoaa furfuryl alcohol, and wherein the distillation is conducted under a vacuum.

10. The process of preparing an initial, fusible, soluble, furfuryl alcohol resinous condensation product which comprises dissolving an active acid catalyst in furfural, the amount of furfural not exceeding about 15% based on the weight of the fur'furyl alcohol, adding said furfural solution of the catalyst to furfuryl alcohol, reacting said mixture under a vacuum to form a furfuryl alcohol condensation product while controlling the temperature of said reaction mix by a substantial balance between the loss of heat from evaporation and the production of heat by reaction.

11. The process of claim 10 wherein the acid catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about 005% and 1% based on the weight of the furiuryl alcohol, and wherein the vacuum distillation employed is continued to produce the substantially anhydrous product.

12. The process of preparing an initial, fusible, soluble, furfuryl alcohol resinous condensation product which comprises dissolving an active acid catalyst in furfural, the amount of furfural not exceeding about 15% based on the weight of the furiuryl alcohol, adding said furfural solution of the catalyst to furfuryl alcohol, reacting said mixture to form a furiuryl alcohol condensation product, during said reaction cooling said reaction mix, neutralizing said condensation product, and distilling said condensation product to produce a substantially anhydrous product.

13. The process of claim 12 wherein the acid catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about 0.05% and 1% based on the weight of the furfuryl alcohol, and wherein the distillation is conducted under a vacuum.

14. The process of preparing an initial, fusible, soluble, furfuryl alcohol resinous condensation product which comprises dissolving an active acid catalyst in furfural, the amount of iurfural not exceeding about 15% based on the weight of the furfuryl alcohol, adding said furfural solution of the catalyst to furfuryl alcohol, reacting said mixture under a vacuum to form a iurfuryl alcohol condensation product while controlling the temperature of said reaction mix by a substantial balance between the loss of heat from evaporation and the production of heat by reaction, neutralizing said condensation product, and distilling said condensation product to produce a substantially anhydrous product.

15. The process f claim 14 wherein the acid catalyst is a strong acid catalyst, wherein the amount of strong acid catalyst added is between about 0.05% and 1% based on the weight of the iurfuryl alcohol, and wherein the distillation is conducted under a, vacuum to produce a substantially anhydrous product.

WILLIAM H. ADAMS, JR.

REFERENQES CITED The following references are of record in the Fiedler Apr. 4, 1944 

